(1) Field of the Invention:
The present invention relates to a welding electrode and more particularly to a coated welding electrode containing chromium in which the content of Na.sub.2 O and K.sub.2 O acting as a binder for a coating flux composition is reduced to a low level, whereby amounts of fumes generated at the welding step, especially the amount of toxic soluble Cr contained in such fumes, are suppressed and minimized.
(2) Description of the Prior Art:
Japanese Patent Publication No. 20477/63 (to Kobe Steel Ltd.) discloses an attempt to reduce the toxicity of fumes generated at the welding step using a low hydrogen welding electrode by reducing the content of K based on the chemical causal relation between CaF.sub.2 and K. This prior art reference, however, has no description about the chemical causal relation between Na and Cr.
U.S. Pat. No. 2,983,632 (to The British Oxygen Co. Ltd.) discloses a coated welding electrode of which a flux comprises titanium, lime stone, iron powder and a binder. It is indefinite whether or not Na and K are contained in the flux of this coated welding electrode, but as will be apparent from various literature references circulated at the time of filing of the above U.S. Patent, in welding electrodes proposed and manufactured in those days, at least 1% of sodium silicate (Na.sub.2 SiO.sub.3 ) based on the total flux was ordinarily contained.
As the welding material in which the content of (Na.sub.2 O + K.sub.2 O) is lower than 1% based on the flux, a flux cored electrode (compsite wire is disclosed in U.S. Pat. No. 3,531,620 (to Kobe Steel Ltd.). In this flux cored electrode, however, since the flux is supported by a metal hoop, it is unnecessary to apply the flux around the core by using a binder as in the case of a flux coated electrode. Accordingly, problems to be solved in a flux cored electrode as disclosed in the above U.S. patent are substantially different from problems to be solved in a flux coated electrode as intended in the present invention.